Re: copy offload support in Linux - new system call needed?

[Ric Wheeler <ricwheeler-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 12/14/2011 02:59 PM, Jeremy Allison wrote:
> On Wed, Dec 14, 2011 at 02:22:07PM -0500, Ric Wheeler wrote:
>> Back at LinuxCon Prague, we talked about the new NFS and SCSI
>> commands that let us offload copy operations to a storage device
>> (like an NFS server or storage array).
>>
>> This got new life in the virtual machine world where you might want
>> to clone bulky guest files or ranges of blocks and was driven
>> through the standards bodies by vmware, microsoft and some of the
>> major storage vendors. Windows8 has this functionality fully coded
>> and integrated in the GUI, I assume vmware also uses it and there
>> are some vendors who announced support at the SNIA SDC conference.
>>
>> We had an active thread a couple of years back that came out of the
>> reflink work and, at the time, there seemed to be moderately
>> positive support for adding a new system call that would fit this
>> use case (Joel Becker's copyfile()).
>>
>> Can we resurrect this effort? Is copyfile() still a good way to go,
>> or should we look at other hooks?
> Windows uses a COPYCHUNK call, which specifies the
> following parameters:
>
> Definition of a copy "chunk":
>
> hyper source_off;
> hyper target_off;
> uint32 length;
>
> and an array of these chunks which is passed
> into their kernel.
>
> This is what we have to implement in Samba.
>
> Jeremy.

This is a public pointer to the draft NFS proposal:

http://tools.ietf.org/id/draft-lentini-nfsv4-server-side-copy-06.txt

The T10 site has some click through that I was not too happy about agreeing to. 
NetApp (Fred Knight) had some nice presentations that he presented about how 
SCSI does this in two different ways...

Ric



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